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Coexistence of Solid and Supercooled Liquid COEXISTENCE OF SOLID AND SUPERCOOLED LIQUID. THERMODYNAMIC EQUILIBRIUM AND DYNAMICS A Thesis Presented to the Faculty of the Graduate School of Cornell University in Partial Fulfillment of the Requirements for the Degree of Master of Science by Antoine Marc Jean Robin August 2018 © 2018 Antoine Marc Jean Robin ALL RIGHTS RESERVED ABSTRACT We study the thermodynamic equilibrium between supercooled liquid and solid using a homemade MEMS device called microtensiometer to directly measure the pressure and temperature of a macroscopic volume of supercooled liquid in equilib- rium with solid. Our measurements on water are consistent with the generalized Clapeyron equation, which predict the relation between the pressure of the liq- uid, the pressure of the solid and the temperature at equilibrium. We also report and discuss remarkable behaviors in the kinetics of equilibration. We found that the equilibration time to reach chemical equilibrium can vary by several orders of magnitude. To better understand this observation, we do a more careful study of the dynamics of transport of supercooled water into ice using a custom-made microfluidic platform. Our results indicate that the dynamics is slower than the prediction of the generalized Clapeyron equation, assuming that the ice remains at atmospheric pressure. We speculate that the transport impacts the pressure in the ice and leads to an effectively lower driving force. BIOGRAPHICAL SKETCH Antoine obtained his bachelor degree in physics at Ecole´ Normale Sup´erieurede Cachan (France) in 2014. He then obtained the Agr´egationde physique chimie (French master degree in teaching of physics and chemistry) in 2016. Antoine began his PhD in 2016 at Cornell University under the supervision of Drs. Abraham Duncan Stroock (Chemical Engineering, Ithaca), Fernando Escobedo (Chemical Engineering, Ithaca) and Robert Thorne (Physics, Ithaca). iii To Dianea Alice Kohl, for her love. iv ACKNOWLEDGEMENTS I would first like to thank my advisor Dr. Abraham Stroock for his inspiring men- torship and constant support. I would also like to thank my committee members, Dr. Robert Thorne and Fernando Escobedo for their discussions and guidance. I am grateful to Al Kovaleski and Jason Londo for their collaboration on a project to study supercooling in grapevine buds. I am also grateful to my research colleagues. Piyush Jain for his friendship and unconditional support in difficult moments, Olivier Vincent for our trips to nature and scientific discussions, Pierre Lidon for our discussions, Michael Santiago for the three weeks we happily spent in the cleanroom. I also thank Siyu Zhu, Hanwen Lu and Winston Black for their daily benevolence and invaluable help. v CONTENTS Biographical Sketch . iii Dedication . iv Acknowledgements . .v Contents . vi List of Figures . viii 1 Introduction 1 2 Background 2 2.1 Supercooled liquids . .2 2.2 Freezing point depression in confinement . .3 2.2.1 Freezing temperature and Gibbs-Thomson equation . .3 2.2.2 Pressure in the liquid . .6 2.2.3 Ice meniscus . .7 3 Contexts 9 3.1 Soils and frost heave . .9 3.2 Cold hardiness in plants . 10 3.2.1 Freeze tolerance . 11 3.2.2 Freeze avoidance . 12 3.3 Porous solids . 13 4 Study on water 16 4.1 Theory . 16 4.2 Materials and Methods . 19 4.2.1 Description and working principle of microtensiometer . 19 4.2.2 Fabrication, calibration and packaging . 21 4.2.3 Experiment . 24 4.3 Results and discussion . 25 4.3.1 Thermodynamic equilibrium . 25 4.3.2 Kinetics . 27 4.3.3 Failure of the microtensiometer . 29 5 Study on Acetic Acid 31 6 Transport of supercooled liquid into the frozen phase 33 6.1 Materials and Methods . 33 6.2 Results and discussion . 34 7 Future work 36 7.1 Study of cryogenic swelling . 36 7.2 Study on doubly metastable liquid . 37 vi 8 Conclusion 38 Bibliography 39 vii LIST OF FIGURES 2.1 Phase diagram of water . .2 2.2 Freezing point depression in confinement . .3 2.3 Freezing point depression of water . .4 3.1 Basic mechanism of frost heave . .9 3.2 Supercooling in xylem of shagbark hickory tree . 11 3.3 Crysuction and cryogenic swelling . 13 3.4 Deformation of a water saturated porous media in equilibrium with bulk ice . 14 4.1 Theoretical pressure in supercooled water in equilibrium with ice . 16 4.2 Extended phase diagram of water . 17 4.3 Description and working principle of microtensiometer . 20 4.4 Packaging of a sensor . 22 4.5 Pressure calibration . 23 4.6 Temperature calibration . 24 4.7 Experimental setup . 25 4.8 Pressure in the liquid Versus Temperature at equilibrium . 26 4.9 Pressure transient . 27 4.10 Failure of the microtensiometer . 30 5.1 Experiment with acetic acid . 31 6.1 Study of the cryosuction dynamics . 33 6.2 Cryosuction dynamics . 34 7.1 Study of cryogenic swelling with a microtensiometer . 36 viii CHAPTER 1 INTRODUCTION Coexistence of solid and supercooled liquid (i.e. liquid colder than bulk freezing temperature) has important consequences in a variety of contexts. Liquid satu- rated concrete swells and cracks at subfreezing temperature, causing severe damage to roads and buildings. In soils, warm water from the ground water migrates to- wards frozen region, causing an upwards displacement of the soil that disrupts infrastructures. Also, plants that live in cold regions are able to survive winter thanks to extracellular ice, which is used to pull liquid out of living cells to pre- serve them from freezing. It is a well-known fact that confined liquids freeze at lower temperature than the bulk and the depression of the freezing point has been extensively characterized. However, little attention has been devoted to the liquid phase when it coexists with the solid. Better understanding of solid/supercooled liquid equilibrium is crucial to improve protection of infrastructures and crops against frost damage. In this thesis, we help filling this gap in the literature by providing direct measurements of the pressure of a macroscopic volume of liquid in equilibrium with the solid phase at different degrees of supercooling. We show that as the temperature drops and the liquid gets more supercooled, its pressure decreases and becomes negative. We also provide comprehensive theoretical cal- culations of the state of the liquid, which very well reproduces the experimental data. The experiments were done using a homemade MEMS device called a mi- crotensiometer, in which a macroscopic volume of liquid can equilibrate with the solid phase through a nano-porous membrane. 1 CHAPTER 2 BACKGROUND 2.1 Supercooled liquids Figure 2.1: Phase diagram of water. Water at a pressure of 1 bar is supercooled when its temperature is lower than the corresponding freezing temperature: 0 ◦C. A volume of liquid at pressure Pl is supercooled when its temperature is such that Tl ≤ T0(Pl), where T0 is the temperature of coexistence of liquid and solid. For example, water at 1 bar is supercooled when its temperature is less than 0 ◦C (see Figure 2.1). Supercooling is a metastable state, any small perturbation will trigger freezing. In practice, moderate supercooling can be easily achieved if the container has smooth, clean walls and care is taken not to mechanically disturb the liquid. Physically, supercooling exists because the nucleation of the ice phase requires to overcome an energy barrier. This energy barrier decreases with increas- ing supercooling. At the temperature of nucleation, the barrier can be overcome and the water freezes spontaneously. The energy barrier depends on the freezing process. The highest energy barrier corresponds to homogeneous nucleation where the ice nucleates in the bulk liquid. For water, the temperature of homogeneous 2 nucleation is −38 ◦C. This energy barrier can be significantly decreased if the solid nucleates on a hydrophobic surface (heterogeneous nucleation). In practise, it is difficult to supercool water to the temperature of homogeneous nucleation. 2.2 Freezing point depression in confinement 2.2.1 Freezing temperature and Gibbs-Thomson equation Figure 2.2: Freezing point depression in confinement. The liquid is confined in a cylindrical pore of radius r and the pore mouth is covered with macroscopic ice at pressure Ps. The freezing transition occurs at temperature Tf which is lower than the bulk equilibrium temperature. Tf ≤ T0(Ps). When the temperature is above T f, the interface between the liquid and the solid forms a meniscus. θ is the angle between the wall the interface. In confined media, the freezing point is depressed relative to the bulk when the liquid wets the wall [2]. More precisely, liquid confined in a narrow pore open to macroscopic solid will freeze at lower temperature than the bulk (see Figure 2.2). This can be explained by a simple thermodynamic argument. The freezing point depression comes from the non-negligible contribution of the interfacial energies to the Gibbs Free Energy relative to the volumetric term, which modifies the equilibrium. This phenomenon is typical in porous media. For example, freezing point depression is similar to capillary evaporation, where liquid confined in a pore open to vapor evaporates at a lower vapor pressure than the bulk saturation 3 Figure 2.3: Freezing point depression of water (reproduced from [1]). Freezing point depression (open symbols) and melting point depression (full symbols) of water in cylindrical silica nano-pores measured by DSC. Rs is an effective radius equal to Rs = R − t where R is the radius of the pore and t is interpreted as the thickness of a non-freezing layer. This non-freezing layer is typically two mono- layers of water molecules thick. With this correction, the data is in very good agreement with the Gibbs-Thomson equation. pressure. The freezing temperature Tf can be found by comparing the Gibbs free energies of the frozen and unfrozen states (which would be respectively the right and left drawings in Figure 2.2).
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